Ubuntu 12.04 64. Hardware failure (motherboard) led me to build a new machine, and I took the opportunity to do a fresh install of Ubuntu (first one was a learning experience). I moved the raid disks over and am seeing them in Disk Utility as /dev/sdb and /dev/sdc with their volumes listed as "RAID Component".
However, when I try to mount them like so
sudo mdadm --assemble /dev/md0 /dev/sdb /dev/sdc
I get this error
mdadm: Cannot assemble mbr metadata on /dev/sdb mdadm: /dev/sdb has no superblock - assembly aborted
Edit with solution:
I followed the instructions found here: Move RAID1 to new machine
In effect, I had to disconnect the drives during the installation process, then the system detected the properly once it was up and running.